1. Field of the Invention
The present invention relates to a radiation detecting apparatus, a scintillator panel, a radiation detecting system, and a method for forming a scintillator layer by deposition; and particularly relates to the scintillator panel, the radiation detecting apparatus, the radioactive rays detection system, which are used in radiographing used in medical diagnosis equipment and non-destructive inspection equipment, and the method for forming a scintillator layer by deposition. In the present specification, “radiation” shall include corpuscular rays such as X-rays, gamma-rays, and alpha-particles and beta-particles. In addition, the “scintillator” shall be a device that converts incident radiation such as X-rays and gamma-rays to light having a wavelength range that can be sensed by a photoelectric conversion element.
2. Description of the Related Art
A radiation detecting apparatus conventionally used in general radiographing uses a radio-sensitized paper having a scintillator layer which converts X-rays into light, and a radiation film having a photosensitive layer.
However, a digital radiation detecting apparatus has been recently developed which has a scintillator layer and a two-dimensional photodetector including photoelectric conversion elements. The digital radiation detecting apparatus facilitates image processing because the obtained data is digital and the data can be shared among multiple persons, when the data is taken into a networked computer system. In addition, if the image digital data is saved in a magneto-optical disk or the like, the digital radiation detecting apparatus can remarkably reduce the storage space required, compared to the case of saving image data in a film, and has an advantage of facilitating a search for past images. In addition, the digital radiation detecting apparatus can reduce the dosage of exposure to radiation for the patient, because a digital radiation detecting apparatus having characteristics of high sensitivity and high sharpness has been proposed along with the progress of the apparatus.
For instance, International Publication Number WO 98/036290 discloses a digital radiation detecting apparatus that has a scintillator layer which is produced with a vacuum deposition technique and includes crystals of cesium iodide (hereafter referred to as CsI) grown into a columnar shape, connected with a photodetector directly or through a protection film. A thus configured digital radiation detecting apparatus can be made with improved sensitivity and sharpness in comparison with that provided with a scintillator layer having conventional scintillators made of granular crystals assembled together.
In addition, International Publication Number WO 99/066350 discloses a digital radiation detecting apparatus having a configuration of adhesively bonding a CsI surface of a scintillator prepared, for instance, by vapor-depositing CsI on a base plate, to a photodetector (which is not shown in the drawings).
A columnar crystal of CsI or the like, which forms a scintillator layer, has properties of absorbing external moisture and deliquescing. A scintillator layer having absorbed moisture deteriorates in its light emission properties and sharpness. For this reason, the above-described conventional radiation detecting apparatus or scintillator panel has a moisture proof protective film for preventing the entry of external moisture.
In addition, a radiation detecting apparatus disclosed in U.S. Pat. No. 4,820,926 has an outermost layer containing only the activator of Tl formed on a light emission material layer.
However, it has been demanded to further improve a moisture-proof effect. Particularly, radiation detecting apparatus for use in a hostile environment like a high-temperature and high-humidity environment has been required to have an improved moisture-proof effect.